Diet is a subjective matter and you really need to understand that each body is different so the needs varies. Even for the same person, the nutritional requirements also changes as our body is constantly changing through age, activity level that we engage in, special stages in life such as pregnancy, puberty and old age.
What I am sharing here are some general and broad principles and guidelines that I use to help me plan and adjust my diet. I do have a sensitive GUT and have suffered from a history of gastric woes and bloatedness so I tried out various methods which helped me ... more on it as a separate topic as digestion is not only affected by the food we consume (as you are aware now). For the guide, you would need to trial and error and always honour your body's response to adjust your diet plan accordingly.